This invention relates in general to safety belt tensioning and rewinding means for retractors employed for storing safety belts or webbing of safety harnesses utilized in vehicles for restraining a passenger in his seat during emergency conditions. More specifically, the present invention in safety belt tensioning and rewinding means relates to devices for applying a low tension on the safety belt when unwound or protracted to a position of use about a vehicle occupant yet provide for a full winding of the belt under the stronger bias of a main rewind spring when the belt is not in a position of use.
Emergency locking retractors normally used in safety harness systems employed in vehicles currently are of the emergency locking type, i.e. the retractor locks against further belt unwinding or protraction only in the event of an emergency condition which may be sensed due to strap acceleration as the persons body moves forward pulling the strap out of the retractor or in response to changes in vehicle acceleration sensed by an inertia sensor or mass associated with the retractor. In such emerency locking retractors, the seat belt webbing or belt is free to move in and out under normal occupant movement subject to the rewind bias of the retractor rewind spring. Tension applied to the belt by virtue of the bias of the rewind spring required for rewinding long lengths of webbing or safety belt employed in safety harness systems can be objectionable to the user. Therefore, various arrangements have been made heretofore for reducing the tension applied to the belt by the rewind spring when the belt is placed in use.
Exemplary of such prior attempts to provide a tension free seat belt retractor is U.S. Pat. No. 3,834,646 wherein the belt tension is completely relieved by means activated by belt manipulation to hold the belt storage reel against retraction. Exemplary of a reduced tension effect for the seat belt are copending applications for U.S. Pat. Ser. No. 701,504 filed July 1, 1976 and application Ser. No. 706,772 filed July 19, 1976. In the retractors of these prior co-pending applications, rewind spring means and low tension applying "low tension zone" spring means are provided coaxially of one another in the retractor for conjugate and/or separate action on the associated reel as explained more fully in such applications. However, we have found it to be desirable to provide a safety belt tensioning and rewinding retractor wherein the low tensioning and rewinding means may be provided in a laterally disposed relative relation in order to allow for a more compact retractor construction and wherein the second biasing means operates in a novel and more fascile manner in association with the reel and first biasing means than those of our prior attempts.